Recovery of phosphate ores in the modified three-product column (3PC) flotation cell

• Concentrates in the C3P column were high in apatite with low impurities contents.
• The higher the wash water flux the lower the iron and silica impurities in flotation concentrates.
• The third product quality suggests its recycling to enhance overall recovery.
• A linear relationship between holdup values and with the bubble superficial area flux was encountered.

This work details the results obtained for the rougher flotation of phosphates in a modified flotation cell known as a three-product column (3PC), at both the laboratory and pilot plant scales. Results were compared to a conventional column cell-CCC. The 3PC cell separates the drained (rejected) particles from the froth zone (third product) and uses a secondary wash water system between the feed and the froth zone (II). Bench-scale studies measured the effect of the two water surface rates on mass and metallurgical recoveries and concentrate grades (P2O5, Fe2O3, and SiO2) in all the flows. At pilot scale, the influence of wash water (JW2) and column design on the flotation separation parameters was studied. Results showed that, compared with the conventional column cell (CCC), the 3PC yielded, in all cases, clean high-grade concentrates, with a minor concentration of impurities (Fe2O3 and SiO2). Concentrate recoveries ranged from 40% to 70% for apatite and were lower when compared to CCC, but it is believed that the third product could be recycled to the fee. This drop-back product operating with JW2 = 0.0 cm s−1 might yield 5–10% extra in apatite recoveries and enhancing this JW2 values, the apatite recovery decreased by 0.5–3% but rejection of impurities was very high. Results appear to show that the 3PC may be used as a rougher-flash or Cleaner unit with an optional recycle of the third product into the rougher or simply discarding it. Data on the influence of some cell design and gas dispersion parameters on process efficiency are reported, and the potential practical applications for this type of cell are envisaged.